You are looking at the HTML representation of the XML format.
HTML is good for debugging, but is unsuitable for application use.
Specify the format parameter to change the output format.
To see the non HTML representation of the XML format, set format=xml.
See the complete documentation, or API help for more information. 
<?xml version="1.0"?>
<api>
  <query>
    <pages>
      <page ns="0" title="API" missing="" />
      <page pageid="1" ns="0" title="Main Page">
        <revisions>
          <rev user="Rvita" timestamp="2021-10-12T17:41:05Z" comment="" contentformat="text/x-wiki" contentmodel="wikitext" xml:space="preserve">&lt;big&gt;'''Curation Manual.'''&lt;/big&gt;

[[Data Field Descriptions]]

[[Curation Manual2.0]]

[[IEDB Inclusion Criteria]]

[[Disease Specific Rules]]

[[CEDAR/Cancer Specific Rules]]

[[Non-peptidic Specific Rules]]

[[Appendix]]

== Help Section ==
* [http://www.mediawiki.org/wiki/Help:Configuration_settings Configuration settings list]
* [http://www.mediawiki.org/wiki/Help:FAQ MediaWiki FAQ]
* [http://meta.wikimedia.org/wiki/Help:Contents User's Guide]
* [http://en.wikipedia.org/wiki/Wikipedia:Extended_image_syntax Image Syntax]
* [http://en.wikipedia.org/wiki/Help:Table Table Creation]
* [http://en.wikipedia.org/wiki/Wikipedia:How_to_edit_a_page How To Edit a Page]
* [http://meta.wikimedia.org/wiki/Help:User_rights User Rights]
* [http://www.w3schools.com/html/ HTML Tutorial]</rev>
        </revisions>
      </page>
    </pages>
  </query>
</api>